1. Field of the Invention
The present invention relates to apparatus for detecting fuel-vapor gas leaks in vehicle internal combustion engines.
2. Description of the Related Art
Conventional apparatus for detecting fuel-vapor gas leaks are disclosed in Japanese Laid-Open Patent Publication 2001-12319 and U.S. Pat. No. 6,112,728. Japanese Laid-Open Patent Publication 2001-12319 (pages 2-6, FIG. 1), for example, discloses a configuration for supplying pressurized air to a purge line and a fuel tank by means of an air pump, after an internal combustion engine is halted, and for judging a leakage amount according to the operating current of the air pump drive motor.
Since the conventional apparatus for detecting fuel-vapor gas leaks are configured for driving the air pump and supplying the pressurized air to the purge line and the fuel tank after the internal combustion engine is halted, and for judging the leakage amount according to the operating current of the air pump drive motor, the air pump, the drive motor and peripheral pipes are needed and the configuration is complex. Since internal pressure of the purge line and the fuel tank are indirectly measured according to the operating current of the air pump drive motor, there is a limit to the precision of the judgment. Moreover, it is necessary to operate the air pump until a predetermined internal pressure is obtained, since there are problems that battery will consume in the leak detection operation after the internal combustion engine is halted; and that unpleasant sounds are given by the leak detection air pump operation.